Fluidized retorting of oil shale



United States Patent O US. Cl. 20811 7 Claims ABSTRACT OF THE DISCLOSUREOil shale is contacted with hot hydrogen in a fluidized system underconditions to conserve heat, to give increased yields and to produceproducts which are susceptible to removal of nitrogen. The hot hydrogencon-.

taining gas is produced from the cracking of a heavy residue recycle inthe presence of the hydrogen containing gas. The cracking takes place ina separate zone and supplies at least a portion of the heat necessaryfor the retorting of the shale.

FIELD OF THE INVENTION The present invention is direced to retorting ofoil shale. More particularly, the invention is concerned with thefluidized retorting of oil shale. In its more specific as pects, theinvention is concerned with the fluidized retorting of oil shale bycontact of the fluidized oil shale with a hot free hydrogen-containinggas.

DESCRIPTION OF THE PRIOR ART It is known to retort oil shale underfluidized conditions. It is also known to retort oil shale by contact ofoil shale in a bed with hot hydrogen. The U.S. patents listed belowconstitute the prior art considered with respect to the presentinvention:

None of the aforementioned prior art teaches the retorting of oil shalewith hot hydrogen in a fluidized system. Neither does the prior artteach the production of a product from retorting in the presence ofhydrogen in a fluidized system from which nitrogen is readily removed.The prior art also does not teach that oil shale particles having smalldiameters such as oil shale fines may be retorted in a fluidized system.

SUMMARY The present invention may be briefly described and summarized asinvolving the retorting of crushed oil shale in which a hot freehydrogen-containing gas is employed to retort the crushed oil shale andin which the crushed oil shale is introduced into and flows seriallythrough a preheating zone, retorting zone, and a cooling zone. In thepresent invention, crushed oil shale including particles havingdiameters less than about 4 to about inch, preferably less than A inch,is flowed counter-currently to free hydrogen-containing gas underfluidized conditions to form the crushed oil shale into fluidized bedsin each of said zones and to decompose kerogen in the crushed oil shaleto vaporized shale oil in said retorting zone. A product is recoveredfrom the preheating zone comprising shale oil and freehydrogen-containing gas. The product is separated into shale oil whichis recovered and is distilled to recover a heavy residue from the shaleoil boiling above about 800 F. which is admixed with freehydrogen-containing gas and subjected to cracking conditions to crackthe heavy residue and to form the free hydrogen-containing gas used inretorting the crushed oil shale. By operating in this manner, heat isconserved and cracking of the heavy residue provides a shale oil fromwhich nitrogen is readily removed. Heat from consumption of hydrogen inthe retorting zone provides at least a portion of the heat of reactionfor retorting the crushed oil shale and finally increased yields areobtained.

BRIEF DESCRIPTION OF THE DRAWING DESCRIPTION OF THE PREFERREDEMBODIMENTS Referring now to the drawing, numeral 11 designates apreheating zone, numeral 12 designates a retorting zone, and numeral 13designates a cooling zone. Crushed or ground oil shale containing fineparticles having diameters ranging from about 0.1 to about 0.01 inch andhaving diameters less than about to about 3/ inch are introduced intothe system by Way of conduit 14 which may suitably include a lock hoppermechanism for introducing the crushed or ground oil shale. The smalldiameter particles or fines may comprise from about 1% to about 20% byweight of the shale introduced by conduit 14, but ordinarily willcomprise from about 5% to about 15% by weight. In preheating zone 11 thecrushed oil shale is heated to a temperature within the range from about200 to about 500 F., preferably about 300 F., by contact with freehydrogen-containing gas and vapors introduced into zone 11 by line 15from retorting zone 12. The preheated oil shale from zone 11 isdischarged into retorting zone 12 by way of line 16, it being noted thatthe crushed or ground oil shale and the free hydrogencontaining gas andvapors flow counter-current to each other.

In retorting zone 12 the preheating crushed oil shale is retorted at atemperature within the range from about 700 to about 1000 F. by contactwith hot free hydrogencontaining gas, the source of which will bedescribed further. The amount of hot free hydrogen-containing gas mayrange from about 10,000 to about 18,000 cubic feet/ton of crushed oilshale introduced into preheating zone 11. The retorted oil shale isdischarged from zone 12 by way of line 17 into cooling zone 13 whereinit is contacted with cooling free hydrogen-containing gas at ambienttemperatures which is introduced into zone 13 by line 18 from a sourcewhich will be described further while the spent oil shale, containingabout l3% of carbonaceous material, is discharged from zone 13 byconduit 19 on to conveying means such as a conveyor belt for conveyingthe spent oil shale to a waste pile.

In cooling zone 13, the retorted oil shale is cooled to a temperaturewithin the range from about 200 to about 400 F. Preferably the retortedshale is cooled to a temperature of about 225 F.

The free hydrogen-containing gas introduced by line 18 into zone 13 ispreheated to a temperature Within the range from about 650 to about 950F. by contact in zone 13 with the retorted oil shale introduced fromzone 12 by line 17. The preheated free hydrogen-containing gas is thenintroduced by line 20 containing a compressor 20a into a heating meanssuch as a furnace 21 where it is heated in admixture with a suitableamount of heavy residue introduced into line 20 by line 22 from a sourcewhich will be described further. Compressor 20a offsets any pressuredrop in furnace 20. This heavy residue 18 preferably a heavy residuefrom shale oil and is employed in an amount of about 8 to about 15gallons/ton of raw oil shale introduced by conduit 14. A suitable amountmay be about 12 gallons/ton of raw oil shale. The mole ratio of freehydrogen to heavy residue is within the range of to about 50. In furnace21, the hydrogen and heavy residue mixture is subjected to elevatedtemperatures within the range from about 800 to about 1200 P. whichcause hydro-cracking of the heavy residue and heating of the freehydrogen-containing gas. Small amounts of fine shale carried in the gasfrom vessel 13 in line 20 scour and keep clean the tubes in furnace 21.A mixture of hot vapors and hot free hydrogen-containing gas isdischarged from furnace 21 by line 23 into retorting zone 12 at atemperature of about 800 to about 1300 F. for retorting the preheatedoil shale introduced into zone 12 by line 16 and to cause decompositionof kerogen to vaporize shale oil. If desired, a portion of the preheatedhydrogen in line 20 may be introduced by line 20b controlled by valve20c into line 23 by passing furnace 21 to provide flexibility of flowthrough furnace 21. It also may be desirable to flow hot preheatedhydrogen and recycle gas directly from zone 13 to zone 12. To this endline 23a controlled by valve 23b allows all or part or none of thegasses from zone 13 to be introduced directly into zone 12. With thismode of operation compressor 20a would be utilized to introduce makeuphydrogen into furnace 21 allowing compressor 20a to operate with a lowrather than a high temperature inlet as is the case when it is used tooffset pressure drop when moving gas from zone 13 into furnace 21.

When gas is fed directly from zone 13 to zone 12, furnace 21 will have ahigher exit temperature Within the range of about l400 to 1600 F.because of decreased gas flow through it.

Product comprising hydrogen and hydrocarbon vapors including vaporizedshale oil is withdrawn from zone 11 by line 24 containing acondenser-cooler 25 which serves to cool the gases and vapors and toallow a separation between gases and liquids in separation zone 26. Inseparation zone 26, water produced in the operation separates and iswithdrawn from water leg 26a by line 27 controlled by valve 28. Freehydrogen and other gases are separated in zone 26 and withdrawn by line29 for use as will be described further. Hydrocarbons including shaleoil and the products of cracking in furnace 21 are withdrawn by line 30and introduced thereby into a distribution zone 31 which suitably may bea fractional distillation tower provided with all auxiliary means foreffective fractional distillation including vapor-liquid contactingmeans, condensing and cooling means, and the like. By way ofillustration, distribution tower 31 is provided with a heating meanssuch as a steam heating coil 32 to allow fractional distillation of thehydrocarbons into various fractions as may be desired. For example, anoverhead fraction comprising light components is withdrawn by line 33, aside stream of heavier hydrocarbon materials is withdrawn by line 34,and a still heavier fraction which may include gas oil components isrecovered by line 35. Heavy residue having a true boiling point of 800or above may be discharged by line 36 and introduced by branch line 37and line 22 into line 20 for admixture of free hydrogen-containing gasintroduced into furnace 21. If desired, a portion of the heavy residuein line 36 may be discharged from the system by opening valve 38.Likewise, heavy material from another source may be introduced into line20 by opening valve 39 in line 22. If desired, such heavy material maybe introduced into zone 12 by line 39a controlled by valve 3%.

To avoid build up of undesirable gases in the system, from time to timeit may be desirable to discharge a portibn of the recycle gas from line29 by opening valve 40. Make-up hydrogen may be introduced into line 18by opening valve 41 connecting to a source of free hydrogen containinggas.

The free hydrogen-containing gas employed in the present invention maybe pure hydrogen, but preferably .4 is a free hydrogen-containing gascontaining from about to about mole percent of free hydrogen with othercomponents including gaseous or vaporous hydrocarbons and the like suchas 0.5 to 10% of CH C H CO N and CO.

In the practice of the present invention the free-hydrogen-containinggas is flowed through the several zones at a suflicient velocity toprovide fluidized beds. For example, the hydrogen velocity may rangefrom about 1 to about 7 feet/second and preferably about 4 feet/ second.Likewise, the employment of pressure is desirable in the practice of thepresent invention and suitable provision is made to employ a pressurizedsystem which may include a suitable lock hopper device in conduit 14 anda suitable pressure discharge mechanism in conduit 19 to maintain apressure on the system within the range from about 300 to about 800p.s.i.

In the practice of the present invention by employing fluidizedhydroretorting with the hydrogen and the oil shale flowingcountercurrent to each other at pressures from 300 to 800 p.s.i. FischerAssay yields within the range from about to about are obtainable. Yieldand quality data obtainable in the present invention are compared to theconventional Bureau of Mines Also, a light prodct from which nitrogen isreadily removed is obtained. For example, in the present invention theproduct from line 36, after the process has been lined out, may compriseproducts having a true boiling point below about 800 F. from whichnitrogen may be readily removed, or the product obtained from line 35may be subjected to treatment for removal of nitrogen. For example,nitrogen may be removed from any of the product produced in the presentinvention by contact in the vapor phase in the presence of hydrogen witha cobalt molybdate alumina-supported catalyst. The relative ease ofdenitrogenation of shale oil in the standard hydro denitrogenation testis indicated below:

Nitrogen, weight The present invention is also quite advantageous inthat the heat from consumption of hydrogen in the retorting zone 12provides a portion of the heat for reaction in retorting oil shale inretorting zone 12. If the same hydro gen were added to a retorted shaleoil as produced conventionally to improve its quality and decrease itsmolecular weight, the heat of reaction would be removed from theretorting system only at considerable expense which the presentinvention avoids.

Fluidized retoiting employing hydrogen is also quite advantageousbecause fine shale particles from the mining process may be processedwhich heretofore was not possible economically. When employing hothydrogen, sufficient carbon remains on the shale so that the dustnuisance from the spent shale is markedly decreased. Also, in thepresent invention, the hydrogen introduced into cooling zone 13 stripsthe spent or retorted oil shale such that there is little or no oilremaining on the shale.

In the practice of the present invention, it is contemplated that thefurnace 21 may be fired with gases produced in the process as a sourceof fuel, or the spent shale containing carbonaceous material may be thesource of fuel, or other fossil fuels may be used.

The nature and objects of the present invention having been completelydescribed and illstrated and the best mode contemplated set forth, whatI wish to claim as new and useful and secure by Letters Patent is:

1. In a method for restorting crushed oil shale in which a hot freehydrogen-containing gas is employed to retort said crushed oil shale andin which said crushed oil shale is introduced into and flows seriallythrough a preheating zone, a retorting zone, and a cooling zone, thesteps which comprise:

flowing crushed oil shale including particles having diameters less thanabout 0.2. to about 0.3 inch countercurrently through said zones to freehydrogen-containing gas under flow conditions to form said crushed oilshale into fluidized beds in each of said zones and to decompose kerogenin said crushed oil shale to vaporized shale oil in said retorting zone;

recovering a product comprising shale oil and free hydrogen-containinggas from said preheating zone;

separating shale oil from said product and distilling the separatedshale oil to recover a heavy residue from said shale oil boiling aboveabout 800 F.;

admixing free. hydrogen-containing gas with said heavy residue; and

subjecting said admixture to cracking conditions in a separate crackingzone to crack said heavy residue and to form said hot freehydrogen-containing gas for retorting said crushed oil shale.

2. A methodin accordance with claim 1 in which said crushed oil shale isretorted at a temperature within the range from about 700 to 1000 F.

3. A method in accordance with claim 1 in which the flow conditions insaid preheating, reto-rting, and cooling zones includes a velocity ofhydrogen within the range from about 1 to about 7 feet per second.

4. A method in accordance with claim 1 in which the crushed oil shale ispreheated and cooled in said preheating and cooling zones, respectively,to a temperature within the range from about 200 to about 400 F.

5. A method in accordance with claim 1 in which the crushed oil shaleintroduced into said preheating zone contains from about 1% to about 20%of particles having diameters less than about 0.2 to about 0.3 inch.

6. A method in accordance with claim 1 in which said crushed oil shaleis retorted at a pressure within the range from about 300 to about 800p.s.i.

7. A method in accordance with claim 1 in which said hot freehydrogen-containing gas is introduced into said retorting zone at atemperature within the range from about 800 to about 1300" F.

References Cited UNITED STATES PATENTS 3,044,948 7/1962 Eastman et al.208-11 DELBERT E. GANTZ, Primary Examiner T. H. YOUNG, AssistantExaminer US. Cl. X.R. 201-29, 31

